Feedstock Solution Flow Concentration System

ABSTRACT

A feedstock solution flow concentration system, which has a first step for counterflowing or parallel flowing a feedstock solution flow a containing a solute and a solvent b, and a draw solution flow d via a forward osmosis membrane o and transferring the solvent b in the feedstock solution flow a to the draw solution flow d to obtain a concentrated feedstock solution flow c, which is the feedstock solution flow which has been concentrated, and a diluted draw solution flow e, which is the draw solution flow which has been diluted.

FIELD

The present invention relates to a feedstock solution flow concentrationsystem.

BACKGROUND

In various fields, it is sometimes necessary to concentrate a feedstocksolution.

As traditional concentration methods, for example, evaporation methodsand reverse osmosis methods are known.

Since evaporation methods require heating of the feedstock solution,there are concerns about problems such as quality changes due to heatingand shape collapse of solid components.

Since reverse osmosis requires pressurization, when used in a highconcentration feedstock solution, membrane clogging is likely to occur,and there is a limit in that the concentration efficiency is limited bythe capacity of the pressurizing pump.

As a feedstock solution concentration method, the forward osmosis methodis also known. The forward osmosis method is a method of transferring asolvent from a feedstock solution flow to a draw solution by adjoining afeedstock solution flow and a draw solution flow via a forward osmosismembrane. Since the forward osmosis method does not requirepressurization, it is expected that highly efficient concentration canbe continued for long periods of time even when applied to ahigh-concentration feedstock solution.

However, there is a concern that some of the solute components in thefeedstock solution flow may leak into the draw solution flow, wherebythe component composition of the obtained concentrated solution maychange.

In connection thereto, Patent Literature 1 proposes a technology inwhich the feedstock solution flow itself after concentration is used asthe draw solution flow.

Patent Literature 2 proposes a technology in which membrane-permeablesolute components are prevented from leaking from a feedstock solutionto a draw solution flow by including the membrane-permeable solutecomponents in the feedstock solution in the draw solution flow atconcentrations higher than the concentrations thereof in the feedstocksolution.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Publication (Kokai) No. 2016-150308

[PTL 2] WO 2016/21337

SUMMARY Technical Problem

Patent Literature 1 describes that, according to the technologydescribed therein, even if a solute component is mixed from the drawsolution flow to the feedstock solution flow, it is possible to preventadverse effects on the component composition of the obtained concentratesolution.

However, according to this method, in addition to requiring a step ofpreparing a concentrate of the feedstock solution flow as draw solutionflow, there is a concern that the presence of feedstock solution flowson both sides of the forward osmosis membrane may cause clogging of themembrane, whereby the desired concentrate magnification cannot beobtained.

In order to carry out the method described in Patent Literature 1, astep of preparing a concentrate of the feedstock solution flow isrequired. Thus, there is a concern that loss or alteration of componentsin the feedstock solution may occur. When a concentrate solution inwhich loss or alteration of the components thereof has occurred is usedas the draw solution flow, the component balance of the obtainedconcentrate may be disturbed, or the altered components may leak anddiffuse into the feedstock solution flow, whereby the quality of theproduct may be impaired.

According to the method of Patent Literature 2, the membrane-permeablesolute should be included in the draw solution flow at a highconcentration. Thus, it is necessary to prepare a large amount of themembrane-permeable solute. When carrying out the method of PatentLiterature 2, the membrane-permeable solute contained at a highconcentration in the draw solution flow may leak and diffuse in thefeedstock solution flow, and there is a concern that the componentbalance of the obtained concentrate may be lost.

The present invention has been conceived in light of such circumstances.

The object of the present invention is to provide a concentration systemusing a forward osmosis membrane with which the feedstock solution flowcan be concentrated with high efficiency by a simple method, and inwhich the diffusion of solute components in the feedstock solution flowinto draw solution flow is controlled.

Solution to Problem

In other words, the present invention is as described below.

<<Aspect 1>>

A feedstock solution flow concentration system, which has a first stepfor counterflowing or parallel flowing a feedstock solution flowcontaining at least a solute and a solvent and a draw solution flow viaa forward osmosis membrane and transferring the solvent in the feedstocksolution flow to the draw solution flow to obtain a concentratedfeedstock solution flow, which is the feedstock solution flow which hasbeen concentrated, and a diluted draw solution flow, which is the drawsolution flow which has been diluted, wherein

-   -   the draw solution flow contains a draw substance, a common        solute, and a solvent,    -   the solvents of the feedstock solution flow and the draw        solution flow both contain water,    -   the common solute is a solute which is common between the        feedstock solution flow and the draw solution flow and is the        same solute as at least one solute among the solutes contained        in the feedstock solution flow, and    -   the concentration of the common solute in the draw solution flow        is 1% to less than 100% of the concentration of the common        solute in the feedstock solution flow.

<<Aspect 2>>

The system according to aspect 1, wherein the number average molecularweight of the common solute is 15,000 or less.

<<Aspect 3>>

The system according to aspect 1 or 2, wherein the common solute is oneor more selected from an ester, a terpene, a phenylpropanoid, a nucleicacid, a protein, a protein preparation, a vaccine, a sugar, a peptide,an amino acid, a natural product pharmaceutical, a small moleculepharmaceutical, an antibiotic, an antibiotic, a vitamin, an inorganicsalt, a protonic polar organic compound, and an aprotic polar organiccompound.

<<Aspect 4>>

The system according to aspect 3, wherein the common solute comprises:

-   -   a cation having at least one element selected from the group        consisting of sodium, magnesium, phosphorus, potassium, calcium,        chromium, manganese, iron, cobalt, copper, zinc, selenium, and        molybdenum, and    -   an anion having at least one element selected from the group        consisting of oxygen, sulfur, nitrogen, chlorine, and iodine.

<<Aspect 5>>

The system according to any one of aspects 1 to 4, wherein theconcentration of the common solute in the draw solution flow is 6% to96% of the concentration of the common solute in the feedstock solutionflow.

<<Aspect 6>>

The system according to any one of aspects 1 to 4, wherein theconcentration of the common solute in the draw solution flow is 30% to96% of the concentration of the common solute in the feedstock solutionflow.

<<Aspect 7>>

The system according to any one of aspects 1 to 6, further comprising asecond step in which a solvent is separated from the draw solution flowto obtain a concentrated draw solution flow, which is the draw solutionflow which has been concentrated.

<<Aspect 8>>

The system according to aspect 7, further comprising means for using, inthe first step, a draw solution flow prepared by mixing the diluted drawsolution flow obtained in the first step and the concentrated drawsolution flow obtained in the second step.

<<Aspect 9>>

The system according to aspect 7 or 8, wherein the second flow iscarried out using a membrane distillation process using a semipermeablemembrane.

<<Aspect 10>>

The system according to any one of aspects 1 to 9, wherein the forwardosmosis membrane is used in the form of a forward osmosis membranemodule constituted by fiber bundle of a plurality of hollow fibers.

<<Aspect 11>>

The system according to aspect 10, wherein the forward osmosis membraneis composite hollow fibers each having an active separation layercomposed of a thin polymer membrane on an inner surface of a hollowfiber-like porous support membrane.

<<Aspect 12>>

The system according to any one of aspects 1 to 11, wherein thefeedstock solution flow is a food, pharmaceutical, pharmaceuticalingredient, pharmaceutical raw material, or pharmaceutical intermediate.

Advantageous Effects of Invention

According to the present invention, there is provided a system using aforward osmosis membrane with which the feedstock solution flow can beconcentrated with high efficiency by a simple method, and in which thediffusion of solute components in the feedstock solution flow into drawsolution flow is controlled. The present invention can be suitablyapplied to applications such as concentration of foods andpharmaceuticals; treatment of precursor solutions for chemicalsynthesis; and treatment of produced water discharged from shale gas andoil fields.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram detailing an example of the system of thepresent invention.

FIG. 2 is a conceptual diagram detailing another example of the systemof the present invention.

DESCRIPTION OF EMBODIMENTS <<Feedstock Solution Flow ConcentrationSystem>>

The feedstock solution flow concentration system of the presentinvention is:

-   -   a feedstock solution flow concentration system, which has a step        (first step) for counterflowing or parallel flowing a feedstock        solution flow containing at least a solute and a solvent and a        draw solution flow via a forward osmosis membrane and        transferring the solvent in the feedstock solution flow to the        draw solution flow to concentrate the feedstock solution flow,        wherein    -   the draw solution flow contains a draw substance, a common        solute, and a solvent,    -   the solvents of the feedstock solution flow and the draw        solution flow both contain water,    -   the common solute is a solute which is common between the        feedstock solution flow and the draw solution flow and is the        same solute as at least one solute among the solutes contained        in the feedstock solution flow, and    -   the concentration of the common solute in the draw solution flow        is 1% to less than 100% of the concentration of the common        solute in the feedstock solution flow.

The feedstock solution flow concentration system of the presentinvention may further have a step (second step) in which the solvent isremoved from the draw solution flow to obtain a concentrated drawsolution flow, which is the draw solution flow which has beenconcentrated.

First, a summary of the feedstock solution flow concentration system ofthe present invention will be described with referring to FIGS. 1 and 2.

FIG. 1 is a conceptual diagram detailing the feedstock solution flowconcentration system of the present invention having a first step.

In the first step, a feedstock solution flow and a draw solution floware counterflowed or parallel flowed via a forward osmosis membrane andthe solvent in the feedstock solution flow is transferred to the drawsolution flow, whereby the feedstock solution flow is concentrated.

In the first step of the feedstock solution flow concentration system ofFIG. 1, a forward osmosis membrane o is provided, and a unit A whichcarries out a forward osmosis process is used. The interior space of theunit A is bifurcated by the forward osmosis membrane o into a feedstocksolution flow-side space R and a draw solution flow-side space D. Afeedstock solution flow a, which is the concentration target, isintroduced into the feedstock solution flow-side space R of the unit A.A draw solution flow d is introduced into the draw solution flow-sidespace D of the unit A.

The feedstock solution flow a contains a solute Xn and a solvent b. Thedraw solution flow d contains a draw substance Xm, the solute (commonsolute) Xn, and the solvent b. The solute Xn in the feedstock solutionflow a and the solute Xn in the draw solution flow d are the same typeof solute, and are a common solute which is common between both flows.When the feedstock solution flow a contains a plurality of types ofsolutes, the common solute may be a part of the plurality of types ofsolutes or may be the entirety thereof.

When the feedstock solution flow a and the draw solution flow d arecounterflowed or parallel flowed via the forward osmosis membrane o,using the osmotic pressure difference between the two solutions as adriving force, the solvent b in the feedstock solution flow a passesthrough the forward osmosis membrane o and is transferred to the drawsolution flow d side. As a result, a concentrated feedstock solutionflow c, which is the feedstock solution flow which has beenconcentrated, and a diluted draw solution flow e, which is the drawsolution flow which has been diluted, are obtained. Though the feedstocksolution flow a and the draw solution flow d are counterflowed in thefirst step of FIG. 1, they may be parallel flowed.

The concentration of the common solute Xn in the draw solution flow d isset so as to be less than the concentration of the common solute Xn inthe feedstock solution flow a. As a result, the osmotic pressuredifference which serves as a driving force for transferring the soluteXn in the feedstock solution flow a to the draw solution flow d side ismitigated. It is believed that since the concentration of the commonsolute Xn of the draw solution flow d is less than that of the feedstocksolution flow a, the common solute Xn is not transferred from the drawsolution flow d to the feedstock solution flow a. As a result, it ispossible to effectively concentrate the feedstock solution flow awithout changing the solute components.

FIG. 2 is a conceptual diagram detailing the feedstock solution flowconcentration system of the present invention having the first step anda second step.

The first step of FIG. 2 is the same as the case of FIG. 1.

In the second step of FIG. 2, the solvent b is removed from the drawsolution flow d to obtain a concentrated draw solution flow f, which isthe draw solution flow which has been concentrated.

In the second step of the feedstock solution flow concentration systemof FIG. 2, a unit B which has a semipermeable membrane p and whichcarries out a membrane distillation process is used. The interior spaceof the unit B is bifurcated by the semipermeable membrane p into aliquid phase L and a gas phase G. The draw solution flow d, which is theconcentration target, is introduced into the liquid phase L of the unitB. The pressure of the gas phase G of the unit B is set to a vacuum.

The draw solution flow d contains the draw substance Xm, the commonsolute Xn, and the solvent b.

The solvent b in the draw solution flow d introduced into the unit B istransferred though the semipermeable membrane p into the vacuum-sidecavity. As a result, the concentrated draw solution flow f and thesolvent b are obtained.

In place of the membrane distillation process, a distillation process orforward osmosis process may be used in the second step.

In the feedstock solution flow concentration system of FIG. 2, the firststep and the second step are connected via a buffer tank.

The buffer tank shown in FIG. 2 has a function of mixing the optimummixing amounts of the diluted draw solution flow e obtained in the firststep and the concentrated draw solution flow f obtained in the secondstep to prepare the draw solution flow d. As a result, in the feedstocksolution flow concentration system of FIG. 2, the draw solution flow dcan be continuously supplied to the unit A of the first step and theunit B of the second step, and thus, concentration of the feedstocksolution flow using a forward osmosis membrane can be continuouslycarried out for long periods of time.

Reference signs r1 and r2 in FIG. 2 are feed pumps, q1 is a heatexchanger, and q2 is a cooling device.

In the feedstock solution flow concentration system of FIG. 2, the firststep and the second step are connected via the buffer tank. However, inthe present invention, this buffer tank is not an indispensablerequirement. For example, the diluted draw solution flow e obtained inthe first step may be directly fed to the unit B of the second step, andthe concentrated draw solution flow f obtained in the second step may beused as the draw solution flow d of the first step.

In the second step, the unit B, which carries out a membranedistillation process, is used. However, in the present invention, in thesecond step, another means which can concentrate the draw solution flowd to obtain the concentrated draw solution flow f may be used. Forexample, an evaporation means other than a membrane distillation processmay be used as the concentration means.

In the second step, the evaporation means other than membranedistillation may be, for example, a distillation process, a vacuumdistillation process, or a natural drying process. However, carrying outthe second step by a membrane distillation process is preferable fromthe viewpoint that the size of the feedstock solution flow concentrationsystem of the present invention can be reduced.

When an evaporation means is used in the second step, since thefeedstock solution flow concentration system adiabatically compressesthe generated vapor of the solvent b into high-temperature compressedvapor, a mechanical vapor recompression (MVR) means may further beprovided. The heat of the high-temperature compressed vapor obtained byMVR can be reused for the evaporation means in the second step.

<<Elements of Feedstock Solution Flow Concentration System>>

A summary of the feedstock solution flow concentration method by thefeedstock solution flow concentration system of the present inventionwas described above. Next, the elements constituting the feedstocksolution flow concentration system of the present invention will bedescribed in detail below.

<Feedstock Solution Flow a>

The feedstock solution flow a is a fluid containing a solute as thetarget of concentration and the solvent b. The feedstock solution flow amay be an emulsion as long as it is a fluid.

Examples of the feedstock solution flow a used in the present inventioninclude foods, pharmaceutical raw materials, seawater, and producedwater discharged from gas and oil fields. However, in the feedstocksolution flow concentration system of the present invention, the drawsolution flow d contains the solute common with the feedstock solutionflow a in a range of 1% to less than 100% of the concentration of thecommon solute in the feedstock solution flow a. By including the commonsolute in the draw solution flow d in this concentration range, thetransfer of the solute from the feedstock solution flow a to the drawsolution flow d can be controlled, and a concentrate in which thecomposition ratio of the feedstock solution flow a is maintained orsubstantially maintained is obtained.

According to or in accordance with the technology of Patent Literature2, if the concentration of the common solute in the draw solution flow dis equal to or greater than the concentration of the common solute inthe feedstock solution flow a, the common solute in the draw solutionflow d leaks and diffuses into the feedstock solution flow a, wherebydisruption of the composition ratio of the components in the obtainedconcentrate often occurs.

In connection thereto, in the feedstock solution flow concentrationsystem of the present invention, the concentration of the common solutein the draw solution flow d is adjusted to a range lower than theconcentration of the common solute in the feedstock solution flow a,specifically, a range of 1% to less than 100%. Thus, leakage anddiffusion of the common solute in the draw solution flow d into thefeedstock solution flow a can be suppressed, and as a result, thecomponent composition ratio of the feedstock solution flow a can beconcentrated as-is or substantially as-is.

Thus, when the feedstock solution flow concentration system of thepresent invention is used for foods, concentration can be carried outwith less loss of aroma components and color components. When the systemof the present invention is used for concentration of pharmaceuticals orthe raw materials thereof, the component balance before and afterconcentration is substantially maintained, whereby concentration can becarried out in a state in which pharmaceutical efficacy is maintained.

For the reasons described above, in the feedstock solution flowconcentration system of the present invention, it is preferable that asolution containing a low molecular weight solute which can pass throughthe forward osmosis membrane (semipermeable membrane) depending on theconditions be used as the feedstock solution flow and at least one ofthe low molecular weight solutes be the solute common between thefeedstock solution flow and the draw solution flow.

The low molecular weight solute may be a material having a numberaverage molecular weight of, for example, 15,000 or less. The numberaverage molecular weight of the low molecular weight solute may be, forexample, 30 or more, 50 or more, 100 or more, 500 or more, 1,000 ormore, 3,000 or more, or 6,000 or more. It may be difficult for thesolute having a number average molecular weight of 6,000 or more to passthrough the forward osmosis membrane, depending on the conditions, butby appropriately setting the implementation conditions, it can passthrough the forward osmosis membrane, and even in such a case, thedesired effect of the present application is advantageously exhibited.

The feedstock solution flow a used in the present invention ispreferably a food, pharmaceutical, pharmaceutical ingredient,pharmaceutical raw material, or pharmaceutical intermediate.

Examples of foods to be concentrated by the feedstock solution flowconcentration system of the present invention include coffee extract,juice (for example, orange juice and tomato juice), alcoholic beverages(for example, wine and beer), dairy products (for example, lactic acidbacteria beverages and raw milk), soup stock (for example, kelp stockand bonito stock), tea extract, aromatic emulsions (for example,emulsions such as vanilla essence and strawberry essence), syrups (forexample, maple syrup and honey), and food oil emulsions (for example,emulsions of rapeseed oil, olive oil, sunflower oil, safflower, andcorn).

(Solute of Feedstock Solution Flow a)

The food, pharmaceutical, pharmaceutical ingredient, pharmaceutical rawmaterial, or pharmaceutical intermediate to be concentrated by thefeedstock solution flow concentration system of the present inventionincludes, as a solute, a useful substance selected from the groupconsisting of nucleic acids, proteins, sugars, peptides, amino acids,antibiotics, natural product pharmaceuticals, small moleculepharmaceuticals, and vitamins. The number average molecular weights ofthese solutes are preferably 100 or more, from the viewpoint of ensuringthe medicinal properties thereof, and are preferably 6,000 or less, fromthe viewpoint of suppression adhesion to the forward osmosis membrane.

Specific examples of the solutes contained in the food, pharmaceutical,pharmaceutical ingredient, pharmaceutical raw material, orpharmaceutical intermediate are described below.

Examples of nucleic acids include oligonucleotides, RNA, siRNA, miRNA,aptamers, decoys, CpG oligos, antisenses, mipomersen, eteplirsen,nusinersen, and pegaptanib.

Examples of proteins include protein preparations and vaccines. Examplesof protein preparations include interferon α, interferon β, interleukins1 to 12, growth hormone, erythropoietin, insulin, granulocyte colonystimulating factor (G-CSF), tissue plasminogen activator (TPA),natriuretic peptides, blood coagulation factor VIII, somatomedin,glucagon, growth hormone-releasing factors, serum albumin, andcalcitonin, and examples of vaccines include hepatitis A vaccines,hepatitis B vaccines, and hepatitis C vaccines.

Examples of sugars include monosaccharides (for example, glucose,fructose, galactose, mannose, ribose, and deoxyribose), disaccharides(for example, maltose, sucrose, and lactose), and sugar chains (forexample, in addition to glucose, galactose, mannose, fucose, xylose,glucuronic acid, and iduronic acid, sugar derivatives such asN-acetylglucosamine, N-acetylgalactosamine, and N-acetylneuraminicacid).

The term “peptide” means a compound in which two or more arbitrary aminoacids are bonded, and the term encompasses dipeptides in which two aminoacids are bonded, tripeptides in which three amino acids are bonded,oligopeptides in which 4 to 10 amino acids are bonded, and polypeptidesin which 11 or more amino acids are bonded. The peptides may be chainedor cyclic.

Examples of amino acids include essential amino acids, non-essentialamino acids, and non-natural amino acids. Examples of essential aminoacids include tryptophan, lysine, methionine, phenylalanine, threonine,valine, leucine, and isoleucine. Examples of non-essential amino acidsinclude arginine, glycine, alanine, serine, tyrosine, cysteine,asparagine, glutamine, proline, aspartic acid, and glutamic acid.

The phrase “non-natural amino acids” means amino acids which are notpresent in nature, and examples thereof include “labeled amino acids” inwhich an arbitrary labeling compound is combined with an amino acidskeleton. The labeling compound may be, for example, a dye, afluorescent substance, a chemical luminescent substance, abioluminescent substance, an enzyme substrate, a coenzyme, an antigenicsubstance, or a protein-binding substance. Specific examples ofnon-natural amino acids include photoresponsive amino acids, opticalswitch amino acids, fluorescent probe amino acids, and fluorescentlabeled amino acids.

Examples of antibiotics include streptomycin and vancomycin.

Examples of natural product pharmaceuticals include cyclosporine,eribulin, rapamycin, and tacrolimus.

Examples of small molecule pharmaceuticals include ledipasvir, revlimid,fluticasone, sofosbuvir, rosuvastatin, pregabalin, imatinib, tiotropium,sitagliptin, emtricitabine, altovastatin, clopidogrel, amlodipine,esomeprazole, simvastatin, olanzapine, valsartan, venlafaxine,sertraline, ranitidine, omeprazole, enalapril, nifedipine, fluoxetine,pravastatin, famotidine, captopril, and acetaminophen. Substancessimilar thereto, progenitors, and intermediates thereof may be used. Themolecular weights of the small molecular pharmaceuticals are preferably2,000 or less.

Examples of vitamins include vitamin A, B-group vitamins, and vitamin C,and encompasses derivatives and salts thereof. Examples of B-groupvitamins include vitamin B6 and vitamin B12.

(Common Solute)

At least one solute included in the feedstock solution flow a is alsocontained in the draw solution flow d. This solute, as used herein, isreferred to below as the common solute Xn, which is common between thefeedstock solution flow a and the draw solution flow d.

Among the solutes contained in the feedstock solution flow a, examplesof the common solute include esters, terpenes (terpenoids),phenylpropanoids, nucleic acids, proteins, protein preparations,vaccines, sugars, peptides, amino acids, natural productpharmaceuticals, small molecule pharmaceuticals, antibiotics,antibiotics, vitamins, inorganic salts, protonic polar organiccompounds, and aprotic polar organic compounds. By using one or more ofthese as the common solute, a concentrated food having an excellentflavor in which the composition of the aromatic components ismaintained, or a concentrated pharmaceutical in which the composition ofthe medicinal ingredients is maintained and the medicinal effect ismaintained is obtained, which is preferable.

As specific examples thereof:

-   -   examples of esters include ethyl butyrate, ethyl isobutyrate,        methyl 2-methylbutyrate, and ethyl methylbutanoate;    -   examples of terpenes include α-pinene, β-pinene, sabinene,        myrcene, cymene, ocimene, terpinene, linalool, borneol, thymol,        α-ionone, β-ionone, γ-ionone, and β-citronellol; and    -   examples of phenylpropanoids include cinnamic acid,        3,4-dihydroxycinnamic acid (also referred to as caffeic acid),        eugenol, anethole, sesamin, lignans, lignin, and cinnamyl        acetate.

The inorganic salts may be a salt comprising a cation having at leastone element selected from the group consisting of sodium, magnesium,phosphorus, potassium, calcium, chromium, manganese, iron, cobalt,copper, zinc, selenium, and molybdenum, and

-   -   an anion having at least one element selected from the group        consisting of oxygen, sulfur, nitrogen, chlorine, and iodine,        and is preferably selected from alkali metal halides, alkali        metal carbonates, alkali metal nitrates, alkali metal sulfates,        alkali metal sulfites, alkali metal thiosulfates, alkaline earth        metal halides, alkaline earth metal carbonates, alkaline earth        metal nitrates, alkaline earth metal sulfates, alkaline earth        metal sulfites, and alkaline earth metal thiosulfates, as well        as various ammonium salts.

Specific examples of inorganic salts include sodium chloride, potassiumchloride, magnesium chloride, calcium chloride, sodium sulfate,magnesium sulfate, sodium thiosulfate, sodium sulfite, ammoniumchloride, ammonium sulfate, and ammonium carbonate.

Specific examples of the nucleic acids, proteins, protein preparations,vaccines, sugars, peptides, amino acids, natural productpharmaceuticals, small molecule pharmaceuticals, antibiotics,antibiotics, and vitamins preferably used as the common solute includethose exemplified above as solutes included in the feedstock solutionflow.

Examples of protonic polar organic compounds include n-butanol,isopropanol, nitromethane, ethanol, methanol, and acetic acid; and

-   -   examples of aprotic polar organic compounds include        N-methylpyrrolidone, tetrahydrofuran, acetone,        dimethylformamide, acetonitrile, and dimethyl sulfoxide. These        protonic polar organic compounds and aprotic polar organic        compounds can be used as the common solute of the present        invention as long as the feedstock solution flow concentration        system of the present invention is not adversely affected        thereby, such as causing defects of the forward osmosis        membrane.

(Solvent of Feedstock Solution Flow a)

The solvent b of the feedstock solution flow is a fluid containing waterand may be water or a mixed solvent of water and a water-soluble organicsolvent, and is preferably capable of dissolving or dispersing the abovesolutes. The solvent b is commonly water.

<Draw Solution Flow d>

The draw solution flow d contains the common solute Xn, which is thesame as at least one of the solutes contained in the feedstock solutionflow a, the draw substance Xm, and the solvent b, and is a fluid whichhas a higher osmotic pressure than the feedstock solution flow a anddoes not significantly denature the forward osmosis membrane o. Thecommon solute Xn is common with a part or all of the solutes Xncontained in the feedstock solution flow a. The concentration of thecommon solute Xn in the draw solution flow d is set to 1% to less than100% of the concentration of the common solute Xn in the feedstocksolution flow a. When the common solute Xn includes a plurality of typesof solutes, the concentration is preferably set, for each type of commonsolutes Xn, so that the concentration in the draw solution flow d is 1%to less than 100% of the concentration in the feedstock solution flow a.

When the feedstock solution flow a and the draw solution flow d asdescribed above come into contact via the forward osmosis membrane o,which is a semipermeable membrane, the solvent b in the feedstocksolution flow a passes through the forward osmosis membrane o and istransferred to the draw solution flow d, and at this time, transfer ofthe common solute Xn in the feedstock solution flow to the draw solutionflow d side is suppressed.

In the present invention, by carrying out the forward osmosis processingsuch a draw solution flow d, the feedstock solution flow a can beconcentrated while maintaining or substantially maintaining thecomponent composition of the solute.

(Common Solute Xn)

As the common solute Xn in the draw solution flow d, one or more may besuitable selected and used from among the solutes contained in thefeedstock solution flow in accordance with the type and properties ofthe feedstock solution flow a, which is the target of concentration, andthe application of the concentrate. Regarding this, refer to theforegoing.

The concentration of the common solute Xn in the draw solution flow d is1% to less than 100% of the concentration of the common solute Xn in thefeedstock solution flow a. From the viewpoint that the elutionsuppression performance of the common solute Xn becomes remarkable, theconcentration of the common solute Xn in the draw solution flow d ispreferably 1% to 99% or 6% to 96% with respect to the concentration(mass %) of the common solute Xn in the feedstock solution flow a. Theratio is more preferably 30% to 96%, and in this range, elution of thecommon solute Xn from the feedstock solution flow a to the draw solutionflow d is suppressed to a practically negligible level.

If the concentration of the common solute Xn in the draw solution flow dis 1% or more with respect to the concentration of the common solute Xnin the feedstock solution flow a, leakage of the common solute Xn fromthe draw solution flow d can be suppressed. If the concentration of thecommon solute X is 6% or more with respect to the concentration of thecommon solute Xn in the feedstock solution flow a, the effect ofsuppressing elution of the common solute Xn from the feedstock solutionflow a to the draw solution flow d is significantly higher, which ispreferable. It is preferable that this ratio be 96% or less, sinceclogging of the forward osmosis membrane o and leakage of the commonsolute Xn from the draw solution flow d are unlikely to occur, and thesolubility or dispersibility of the draw substance Xm in the drawsolution d is improved and a high osmotic pressure can be obtained.

When the draw solution flow d contains a plurality of types of commonsolutes Xn, it is sufficient that one thereamong satisfy the aboveconcentration conditions. However, it is preferable that all of thecommon solutes Xn contained in the draw solution flow d be 1% to lessthan 100% of the concentration (mass %) of the corresponding commonsolute Xn in the feedstock solution flow a.

Even if the common solute Xn is present as ions ionized in the solventb, the concentration of the common solute Xn in the present invention isdetermined based on the value of the formula weight prior to ionization.

(Draw Substance Xm)

The draw substance Xm is a material which is contained in the drawsolution flow d, and imparts the draw solution flow d with a higherosmotic pressure than the feedstock solution flow a.

Examples of the draw substance Xm which can be used in the presentinvention include inorganic salts, sugars, alcohols, and polymers.

Examples of inorganic salts include sodium chloride, potassium chloride,magnesium chloride, calcium chloride, sodium sulfate, magnesium sulfate,sodium thiosulfate, sodium sulfite, ammonium chloride, ammonium sulfate,and ammonium carbonate;

-   -   examples of sugars include general sugars such as sucrose,        fructose and glucose, and special sugars such as        oligosaccharides and rare sugars;    -   examples of alcohols include monoalcohols such as methanol,        ethanol, 1-propanol and 2-propanol, and glycols such as ethylene        glycol and propylene glycol; and    -   examples of polymers include polymers such as polyethylene oxide        and propylene oxide, as well as copolymers thereof.

The examples of the draw substance Xm above partially overlap theexamples of the common solutes Xn. The materials for which the examplesoverlap can be used as the common solute Xn or can be used as the drawsubstance Xm. However, a draw solution flow d containing a certainmaterial as the draw substance Xm cannot be used to concentrate afeedstock solution flow a containing the certain material as the commonsolute Xn. This is because, since the concentration of the common soluteXn in the draw solution flow d is limited to 1% to less than 100% of theconcentration of the common solute Xn in the feedstock solution flow a,it is unlikely that the draw solution flow d will be imparted with ahigher osmotic pressure than the feedstock solution flow a at such lowconcentrations.

The concentration of the draw substance Xm in the draw solution flow dis set so that the osmotic pressure of the draw solution flow d ishigher than the osmotic pressure of the feedstock solution flow a. Aslong as the osmotic pressure of the draw solution flow d is higher thanthe osmotic pressure of the feedstock solution flow a, it may fluctuatewithin that range.

To determine the osmotic pressure difference between two liquids, one ofthe following methods can be used.

-   -   (1) When the two liquids separate into two phases after mixing:        it is determined that a liquid having an increased volume after        the separation into two phases has a higher osmotic pressure; or    -   (2) when the two liquids do not separate into two phases after        mixing: the two liquids are brought into contact with each other        via the forward osmosis membrane o, and it is determined that a        liquid having an increased volume after a certain period of time        has a higher osmotic pressure. At this time, the certain period        of time depends on the osmotic pressure difference, but is        generally in the range of several minutes to several hours.

The common solute Xn along with the draw substance Xm contributes to thegeneration of the osmotic pressure of the draw solution flow d. Thus,for setting of the concentration of the draw substance Xm in the drawsolution flow d, for example, the Van't Hoff formula may be used afterconsidering the concentration of the common solute Xn in the drawsolution flow d.

As a typical example, when water is used as the solvent b and awater-soluble inorganic salt is used as the draw substance Xm, theconcentration of the draw substance Xm in the draw solution flow d canbe, for example, in the range of 15% by mass to 60% by mass.

(Solvent of Draw Solution Flow d)

The solvent of the draw solution flow d is a fluid containing water, ispreferably capable of dissolving or dispersing the common solute Xn andthe draw substance Xm, and is preferably a solvent of the same type asthe solvent b to be separated from the feedstock solution flow a. Forexample, if the solvent of the feedstock solution flow a is water, thesolvent of the draw solution flow d is also preferably water.

(Draw Solution Flow d Preparation Method)

The draw solution flow d used in the present invention can be preparedby dissolving or dispersing the common solute Xn and the draw substanceXm in the solvent b.

As described above, in the feedstock solution flow concentration systemof the present invention, the concentration of the common solute in thedraw solution is 1% to less than 100% of the concentration of the commonsolute in the feedstock solution flow, and may be 1% to 99%, 6% to 96%,or 30% to 96%.

The common solute Xn may be introduced into the draw solution flow d bythe addition of the feedstock solution flow a itself or may beintroduced into the draw solution flow d by the addition of componentscorresponding to the common solute Xn.

When the introduction of the common solute Xn into the draw solutionflow d is carried out by the addition of the feedstock solution flow aitself, it is not necessary to prepare a large amount of concentrate orcommon solute of the feedstock solution flow in advance, whereby thedraw solution flow d can be prepared by a simple means.

The addition of the common solute Xn and the draw substance Xm into thesolvent b may be carried out at any time during which the system isrunning. The addition is preferably carried out, for example, before thedraw solution flow d is introduced into the unit A of the first step orbefore it is introduced into the unit B of the second step, but is notlimited thereto.

Depending on the type of the feedstock solution flow a and the intendedapplication of concentrated feedstock solution flow c, prevention of thetransfer of the common solute Xn from feedstock solution flow a to drawsolution flow d at arbitrary times during system operation may bedesired. In such a case, the present invention includes an embodiment inwhich, for example, first, operation is started with a draw solutionflow d consisting of the draw substance Xm and solvent b, and a commonsolute Xn of predetermined concentration is added to the draw solutionflow d prior to the time at which the prevention of the transfer ofcommon solute Xn is desired.

<First Step>

In the first step of the feedstock flow concentration system of thepresent invention, a forward osmosis process is carried out using theunit A, the interior space of which is separated into two including thefeedstock solution flow-side space R and the draw solution flow-sidespace D, by the forward osmosis membrane o.

<Forward Osmosis Membrane o of Forward Osmosis Unit)

The forward osmosis membrane o of the unit a is a membrane which has afunction of allowing the solvent b to permeate but preventing orinhibiting permeation of the solute.

Examples of the form of the forward osmosis membrane o include ahollow-fiber form, a flat membrane form, and a spiral membrane form.

The forward osmosis membrane o is preferably a composite membrane havingan active separation layer on a support layer (support membrane). Thesupport membrane may be a flat membrane or a hollow fiber membrane.

When a flat membrane is used as the support membrane, the supportmembrane may have an active separation layer on one side or both sidesthereof.

When a hollow fiber membrane is used as a support membrane, it may havean active separation layer on the outer surface or the inner surface ofthe hollow fiber membrane, or on both surfaces.

The support membrane of the present embodiment is a membrane on whichthe active separation layer is supported, and it is preferable that thesupport membrane itself not substantially exhibit separation performancewith respect to the object to be separated. As the support membrane, anyknown microporous support membrane or non-woven fabric can be used.

The preferred support membrane of the present embodiment is amicroporous hollow fiber support membrane. The microporous hollow fibersupport membrane has fine pores having a pore diameter of preferably0.001 μm to 0.1 μm, and more preferably 0.005 μm to 0.05 μm on the innersurface thereof. Regarding the structure from the inner surface of themicroporous hollow fiber support membrane to the outer surface in thedepth direction of the membrane, in order to reduce the permeationresistance of the permeating fluid, it is preferable that the structurebe as sparse as possible while maintaining strength. The sparsestructure of this portion is preferably, for example, a net-likestructure, finger-like voids, or a mixed structure thereof.

The material of the support membrane, particularly the microporoussupport membrane, may be a material which can be molded as a microporoussupport membrane and is not chemically damaged by the monomer or solventused to form the active separation layer, but is not particularlylimited. In the present embodiment, those capable of forming into ahollow fiber-like microporous support membrane are preferable.

As the material of the support membrane, for example, a materialcomposed of at least one selected from polyether sulfone, polysulfone,polyketone, polyetheretherketone, polyphenylene ether, polyvinylidenefluoride, polyacrylonitrile, polyimine, polyimide, polybenzoxazole,polybenzimidazole, and polyamide as a main component is preferable. Amain component of at least one selected from polysulfone and polyethersulfone is more preferable, and using polyethersulfone is particularlypreferable.

As an active separation layer in the flat or hollow fiber-like forwardosmosis membrane o, for example, a layer composed of a thin polymermembrane containing at least one selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene,polypropylene, polyamide, and cellulose acetate as a main component ispreferable since the suppression rate of draw substance is high. A maincomponent of at least one selected from polysulfone, polyether sulfone,polyvinylidene fluoride, polyacrylonitrile, and polyamide is morepreferable, and a polyamide layer is particularly preferable.

The polyamide in the active separation layer can be formed byinterfacial polymerization of a polyfunctional acid halide and apolyfunctional aromatic amine.

The polyfunctional aromatic acid halide is an aromatic acid halidecompound having two or more acid halide groups in one molecule. Specificexamples thereof include trimesic acid halide, trimellitic acid halide,isophthalic acid halide, terephthalic acid halide, pyromellitic acidhalide, benzophenone tetracarboxylic acid halide, biphenyldicarboxylicacid halide, naphthalenedicarboxylic acid halide, pyridinedicarboxylicacid halide, and benzenedisulfonic acid halide and these can be usedalone or as a mixture thereof. Examples of the halide ion in thesearomatic acid halide compounds include chloride ions, bromide ions, andiodide ions. In the present invention, in particular, trimesic acidchloride alone, a mixture of trimesic acid chloride and isophthalic acidchloride, or a mixture of trimesic acid chloride and terephthalic acidchloride is preferably used.

Polyfunctional aromatic amines are aromatic amino compounds having twoor more amino groups in one molecule. Specific examples thereof includem-phenylenediamine, p-phenylenediamine, 3,3′-diaminodiphenylmethane,4,4′-diaminodiphenylamine, 4,4′-diaminodiphenyl ether,3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenylamine,3,5-diaminobenzoic acid, 4,4′-diaminodiphenyl sulfone,3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone,1,3,5-triaminobenzene, and 1,5-diaminonaphthalene, and these may be usedalong or as a mixture thereof. In the present invention, in particular,one or more selected from m-phenylenediamine and p-phenylenediamine cansuitably be used.

Interfacial polymerization of the polyfunctional acid halide and thepolyfunctional aromatic amine can be carried out according to a knownmethod.

Nanoparticles, vesicles, and coating agents may be contained on thesurface or interior or both of the support membrane and the molecularactive layer constituting the forward osmosis membrane of the presentembodiment.

Examples of nanoparticles include open-ended carbon nanotubes,closed-ended carbon nanotubes, carbon fibers, nanofibers, nanowires,nanorods, nanotubes, and metal nanoparticles;

-   -   examples of vesicles include liposomes, polymersomes, and        self-assembled nanostructures (e.g., self-assemblies including        certain transmembrane proteins and detergents); and    -   examples of coating agents include graphene oxide, polyvinyl        alcohol, silver-supported polymers, polydopamine,        polyvinylpyrrolidone, poly(2-hydroxyethyl methacrylate),        cyclodextrin, and silsesquioxane.

In the present embodiment, a hollow fiber-like forward osmosis membraneis preferably used, and in particular, a composite hollow fiber havingan active separation layer composed of a thin polymer membrane on aninner surface of a hollow fiber-like porous support membrane ispreferably used.

As the unit A, a unit in the form of a forward osmosis membrane modulein which a fiber bundle of a plurality of forward osmosis membranes ispreferably housed in a suitable housing is preferably used.

The permeability flux for the solvent b of the forward osmosis membraneo is preferably 1 to 100 kg/(m²× hr). If the permeability flux is lessthan 1 kg/(m²× hr), the solvent b separation efficiency may be impaired,and if it exceeds 100 kg/(m²× hr), the transfer amount of the drawsubstance Xm from the draw solution flow d to the concentrated feedstocksolution flow c via the forward osmosis membrane o may increase.

The permeability flux for the solvent b as used herein means an amountobtained by assigning the amount of the solvent b passing through theforward osmosis membrane o per unit area of the forward osmosis membraneo and per unit time, and is defined by the following formula (1):

F=L/(M×H)  (1)

where F is the permeability flux (kg/(m²× hr)) for solvent b, L is theamount of solvent b permeated (kg), M is the surface area (m²) of theforward osmosis membrane o, and H is the time (hr).

The permeability flux when the solvent b is water is generally referredto as “water permeability”, and can be measured using, for example, purewater as a treatment liquid and 3.5% by mass saline as the draw solutionflow.

(Introduction of Feedstock Solution Flow a and Draw Solution Flow d intoUnit A)

The feedstock solution flow a, which is the object to be concentrated,is introduced into the feedstock solution flow-side space R of the unitA, and the draw solution flow d is introduced into the draw solutionflow-side space D. The directions of these flows may be counterflow orparallel flow.

Though the flow rate of the feedstock solution flow a introduced intothe feedstock solution flow-side space R of the unit A is arbitrary, atypical example includes the range of 50 mL/(m²·min) to 1500 mL/(m²·min)per m² surface area of the forward osmosis membrane in the unit A perminute, and is preferably set to 100 mL/(m²·min) to 1000 mL/(m²·min).

Though the flow rate of the draw solution flow d introduced into thedraw solution flow-side space D of unit A is arbitrary, an examplethereof includes the range of 100 mL/(m²·min) to 5000 mL/(m²·min), andis preferably set to 500 mL/(m²·min) to 2000 mL/(m²·min)

(Temperatures of Feedstock Solution Flow a and Draw Solution Flow d)

In the first step, the temperature of the feedstock solution flow aintroduced into the feedstock solution flow-side space R of the unit Ais not particularly limited. It is not necessary to specifically controlthe temperature. The temperature may be, for example, room temperature.

The temperature of the draw solution flow d introduced into the drawsolution flow-side space D of the unit A is not particularly limited,but is preferably 5° C. to 60° C., and more preferably 15° C. to 40° C.Though the reason is not clear, when the temperature of the drawsolution flow d is less than 15° C. or higher than 60° C., in somecases, the amount of the draw substance Xm transferred from the drawsolution flow d to the feedstock solution flow a via the forward osmosismembrane o is increased.

(Second Step)

The second step optionally used in the solvent separation system of thepresent embodiment is: a step of separating the solvent b from the drawsolution flow d to obtain a concentrated draw solution flow f, which isthe draw solution flow which has been concentrated, and the solvent b.

In the step of separating the draw solution flow d into the concentrateddraw solution flow f and the solvent b, for example, a distillationprocess, a forward osmosis process, or a membrane distillation processcan be used.

The distillation process is a step of adjusting the draw solution flow dto a predetermined temperature, and then passing it through adistillation column to obtain the solvent b from the top of the columnas well as obtaining a concentrated draw solution flow f, which is thedraw solution flow from which the solvent b has removed and which hasbeen concentrated, from the bottom of the column.

The forward osmosis process is a step in which the draw solution flow dis flowed through the forward osmosis membrane so that the solvent bcontained in the draw solution flow d passes through the forward osmosismembrane and thereby separated into the solvent b and the concentrateddraw solution flow f, from which the solvent b is removed.

The membrane distillation process may be carried out, for example, bythe configuration shown as the second step in FIG. 2. In this case, themembrane distillation process is configured such that the separationchamber is divided into the liquid phase L and the gas phase G using thesemipermeable membrane p, and the solvent b contained in the drawsolution flow d passes from the liquid phase L through the semipermeablemembrane to the gas phase G at reduced pressure, whereby the drawsolution flow d can be separated into the solvent b and the concentrateddraw solution flow f.

As a process in the second step, a forward osmosis process using aforward osmosis membrane or a membrane distillation process using asemipermeable membrane p is preferable in terms of small facility size,and a membrane distillation process using a semipermeable membrane p ismore preferable in terms of suppressing the transfer of the drawsubstance Xm from the draw solution flow d to the solvent b.

(Semi-Permeable Membrane p of Membrane Distillation Process)

Examples of the shape of the semipermeable membrane p used in themembrane distillation process include any shape selected from the shapesexemplified above regarding the shape of the forward osmosis membrane oin the first step, and specific examples thereof include a hollow fibershape, a flat membrane shape, and a spiral membrane shape.

The semipermeable membrane p in the form of a flat membrane may becomposed of, for example, a single layer, or may have a support layerand an active separation layer on the support layer. The hollowfiber-like semipermeable membrane p may be, for example, a hollow fibercomposed of a single layer, or may have a hollow fiber-like supportlayer and an active separation layer on an outer surface or an innersurface, or both, of the support layer.

The material of the support layer and the active separation layer in thesemipermeable membrane p may be any material selected from the materialsexemplified above for the forward osmosis membrane o in the first step.

The permeability flux for the solvent b of the semipermeable membrane pis preferably 1 kg/(m²×hr) to 200 kg/(m²× hr). If the permeability fluxis less than 1 kg/(m²× hr), efficient separation of the solvent b may beimpaired, and if it exceeds 200 kg/(m²× hr), the transfer amount of thedraw substance from the draw solution flow d to the solvent b via thesemipermeable membrane p may be increased.

This permeability flux is defined in the same manner as the permeabilityflux for solvent b of the forward osmosis membrane o in the first step.

(Temperature of Draw Solution Flow d Introduced in Membrane DistillationProcess)

It is preferable that the temperature of the draw solution flow d beadjusted to a range of 20° C. to 90° C. prior to introduction into theliquid phase L. If this temperature is less than 20° C., the efficiencyof separation of the solvent b by membrane distillation may be impaired,and if it exceeds 90° C., the amount of the draw substance Xm containedin the draw solution flow d transferred to solvent b via thesemipermeable membrane p may increase.

As the heat source for heating the draw solution flow d, for example, aheat exchanger q1 can be used, or waste heat such as from an industrialprocess can be used. When waste heat is utilized as the heat source, theamount of energy newly consumed for separation of the solvent b can bereduced, which is preferable.

(Gas Phase G in Membrane Distillation Process)

It is preferable that the pressure of the gas phase G of the unit B usedin the membrane distillation process be reduced to a predeterminedpressure. The pressure of the gas phase G may be appropriately setaccording to the scale of the device, the concentration of the drawsolution flow d, and the generation rate of the desired solvent b, butis preferably set to, for example, 0.1 kPa to 80 kPa, and morepreferably 1 kPa to 50 kPa.

Examples the vacuum device for reducing the pressure of the gas phase Gof the unit B include a diaphragm vacuum pump, a dry pump, an oil rotaryvacuum pump, an ejector, or an aspirator.

(Products of Second Step)

As a result of the second step, the solvent b is separated from the drawsolution flow d to produce the concentrated draw solution flow f, whichis the draw solution flow which has been concentrated, and is dischargedfrom the unit B.

The concentrated draw solution flow f can be mixed with the diluted drawsolution flow e to adjust to a predetermined concentration and thenreused as the draw solution flow d. Upon reuse of the concentrated drawsolution flow f, the temperature of the concentrated draw solution flowf may be adjusted using a cooling device q2. Examples of the coolingdevice q2 include a chiller and a heat exchanger.

The solvent b separated from the draw solution flow d by the second stepmay be reused if necessary.

<<Preparation and Use of Draw Solution Flow d>>

The feedstock solution flow concentration system of the presentinvention may further include means for using, in the first step and thesecond step, the draw solution flow d prepared by mixing the diluteddraw solution flow e obtained in the first step and the concentrateddraw solution flow f obtained in the second step.

In the system of FIG. 2, the first step and the second step areconnected via a buffer tank. The buffer tank has a function of mixingthe diluted draw solution flow e obtained in the first step and theconcentrated draw solution flow f obtained in the second step at anoptimum mixing amount to prepare the draw solution flow d.

The draw solution flow d prepared (regenerated) in the buffer tank canbe fed to the first step by a feed pump r1 and to the second step by afeed pump r2 and used in the respective steps.

As a result of such a configuration, the feedstock solution flowconcentration system of the present invention can continuously supplythe draw solution flow d to the unit A of the first step and the unit Bof the second step, and thus, concentration of the feedstock solutionflow using the forward osmosis membrane can be continuously carried outfor long periods of time.

EXAMPLES

Hereinafter, the present invention will be specifically described basedon the Examples, but the present invention is not limited by theExamples.

The following Examples and Comparative Examples were carried out usingthe feedstock solution flow concentration system having theconfiguration shown in FIG. 2.

(Preparation of Feedstock Solution Flow Concentration System)

<Preparation of Unit a Having Forward Osmosis Membrane o>

(Production of Hollow Fiber Support Membrane Module)

A polyether sulfone (product name: “Ultrason”, manufactured by BASF Co.,Ltd.) was dissolved in a N-methyl-2-pyrrolidone (manufactured by WakoPure Chemical Industries, Ltd.) to prepare a 20% by mass hollow fiberspinning stock solution.

A wet hollow spinning machine equipped with a double spinning port wasfilled with the above stock solution, and extruded into a coagulationtank filled with water to form hollow fibers by phase separation. Theobtained hollow fibers were wound on a winding machine. The obtainedhollow fibers had an outer diameter of 1.0 mm and an inner diameter of0.7 mm, and the diameter of micropores on the inner surface thereof was0.05 μm.

These hollow fibers were used as the microporous hollow fiber supportmembrane.

A hollow fiber support membrane module having an effective innermembrane surface area of 0.023 m² was prepared by filling 130 of theabove hollow fiber support membranes into a cylindrical plastic housinghaving a diameter of 2 cm and a length of 10 cm and fixing both endswith an adhesive.

(Production of Unit A, Forward Osmosis Membrane Module)

10 g of m-phenylenediamine and 0.08 g of sodium lauryl sulfate werecharged into a 0.5 L capacity vessel, and further 489.2 g of pure waterwas added for dissolution to prepare 0.5 kg of a first solution used forinterfacial polymerization.

0.8 g of trimesic acid chloride was charged into a separate 1.0 Lvessel, and 399.2 g of n-hexane was added for dissolution to prepare 0.4kg of a second solution used for interfacial polymerization.

The core side (inside of the hollow fiber) of the hollow fiber supportmembrane module manufactured in the “Production of Hollow Fiber SupportMembrane Module” above was filled with the first solution, and afterstanding for 5 minutes, the liquid was withdrawn, whereby the insides ofthe hollow fibers were wetted with the first solution.

Thereafter, the core side pressure was set to normal pressure by a coreside pressure adjusting device, and the shell side pressure was set to areduced pressure of 90 kPa as an absolute pressure by a shell sidepressure adjusting device, and left standing for 5 minutes in thisstate. Subsequently, on the core side, an operation of passing nitrogenat a flow rate of 5 L/min for 5 minutes was carried out to remove theexcess first solution. While the pressure on the shell side wasmaintained at a reduced pressure of 90 kPa as an absolute pressure, thesecond solution was fed into the core side by a second solution feedingpump at a flow rate of 50 mL/min for 2 minutes, and interfacialpolymerization was carried out. The polymerization temperature was setat 25° C.

Nitrogen was then flowed at 40° C. through the core side of the hollowfiber support membrane module for 1 min to transpirate and removen-hexane. Both the shell side and the core side were washed with purewater to produce unit A, which is a module of a hollow fiber-likeforward osmosis membrane o having an active separation layer composed ofa polyamide on the inner surface of the hollow fiber support membrane.

(Preparation of Unit B Having Semi-Permeable Membrane p for MembraneDistillation Process)

23 parts by mass of hydrophobic silica (product name “AEROSIL-R972”,manufactured by Nippon Aerosil Co., Ltd.) having an average primaryparticle diameter of 0.016 μm and a specific surface area of 110 m²/g,31 parts by mass of dioctyl phthalate (DOP), and 6 parts by mass ofdibutyl phthalate (DBP) were mixed with a Henschel mixer, and thereafter40 parts by mass of polyvinylidene fluoride (product name “Solef 6010”,manufactured by SOLVAY Co., Ltd.) having a weight-average molecularweight of 310,000 was added thereto, and the mixture was mixed againwith the Henschel mixer to obtain a mixture. The mixture was pelletizedwith a two-axis kneading extruder.

The obtained pellets were melt-kneaded with the two-axis kneadingextruder at 240° C., and extruded into a hollow fiber-like shape toobtain hollow fibers. At this time, a spinning port for hollow fibermolding was mounted on the extrusion port in the head of an extruderend, and kneading melt was extruded from an annular hole for meltextrusion, and simultaneously, nitrogen gas was ejected from a circularhole for discharging a hollow portion forming fluid inside the annularhole for melt extrusion, thereby extruding into a hollow fiber shape.

The hollow filament was introduced into a water bath (40° C.) at anempty running distance of 20 cm and wound at a rate of 20 m/min.

The resulting hollow filaments were drawn continuously at a rate of 20m/min in a pair of first endless orbital belt drawers and passed througha first heated bath (0.8 m length) controlled to a space temperature of40° C., and then withdrawn at a rate of 40 m/min in a second endlessorbital belt withdrawer and stretched 2.0 times in the length direction.After passing through a second heating tank (0.8 m length) controlled toa space temperature of 80° C., the filaments were cooled while beingperiodically folded at the water surface of a 20° C. cooling water tank.The drawn yarn was then withdrawn at a rate of 30 m/min by a thirdendless orbital type belt drawer, and the drawn yarn was shrunk(relaxed) to 1.5 times in the length direction, and then wound with askein (hank) having a circumferential length of approximately 3 m.Periodic folding at the water surface of the cooling water tank wascarried out by continuously sandwiching the hollow filaments at arotation speed of 170 rpm using a pair of convex/concave rollers havingfour protrusions and lengths of approximately 0.20 m.

The hollow filaments after the above treatment were immersed inmethylene chloride to extract and remove DOP and DBP, and then dried.The hollow filaments were then immersed in 50% by mass aqueous ethylalcohol solution, and then immersed in a 5% by mass aqueous sodiumhydroxide solution for 1 hour at 40° C., thereby extracting and removingsilica. Thereafter, the filaments were washed with water and dried toobtain a hollow fiber membrane. The obtained hollow fibers had an outerdiameter of 1.25 mm and an inner diameter of 0.68 mm, and the diameterof micropores on the inner surface thereof was 0.1 μm. These hollowfibers were used as the semipermeable membrane.

By filling 70 semipermeable membranes composed of the above hollowfibers into a cylindrical plastic housing having a diameter of 2 cm anda length of 10 cm and fixing both ends with an adhesive, unit B, whichis a membrane distillation module having a hollow fiber-likesemipermeable membrane p having an effective inner membrane surface areaof 0.012 m² was produced.

Comparative Example 1

In Comparative Example 1, the forward osmosis unit A prepared above wasused as unit A in the first step, and the membrane distillation unit Bproduced above was used as unit B in the second step.

Water was used as solvent b.

As the draw solution flow d, an aqueous solution containing magnesiumchloride as the draw substance Xm was used, and the magnesium chlorideconcentration in the draw solution flow d was set to 20% by mass.

As the feedstock solution flow a, an aqueous solution containing sodiumchloride was used, and the initial concentration thereof was set to 5.0%by mass.

In the first step, the feedstock solution flow a was flowed into unit Aat a flow rate of 10 mL/min and the draw solution flow d was flowed at aflow rate of 24 mL/min.

In the second step, the draw solution flow d was flowed into unit B at aflow rate of 600 mL/min, and the pressure of the gas phase G of unit Bwas adjusted with a vacuum pump to 10 kPa as an absolute pressure.

The diluted draw solution flow e obtained in the first step and theconcentrated draw solution flow f obtained in the second step were mixedin a buffer tank to prepare a draw solution and reused in the first andsecond steps.

The temperature of the draw solution flow d in the unit A in the firststep was 25° C., the temperature of the draw solution flow d in the unitB in the second step was 65° C., and by carrying out operation for 10hours, concentration of the feedstock solution flow a was carried out.

Comparative Examples 2 to 10

Concentration of the feedstock solution flow a was carried out accordingto the same procedure as in Comparative Example 1, except that the typeand concentration of the draw substance Xm in the draw solution flow dand the solute Xn in the feedstock solution flow a were changed asdescribed in Table 1.

Example 1

Concentration of the feedstock solution flow a was carried out accordingto the same procedure as in Comparative Example 1, except that a mixtureobtained by adding sodium chloride at a concentration of 4.8% by mass ascommon solute Xn with the feedstock solution flow a together withmagnesium chloride as the draw substance Xm was used as the drawsolution flow d.

Examples 2 to 15

Concentration of the feedstock solution flow a was carried out accordingto the same procedure as in Example 1, except that the type of the drawsubstance Xm in the draw solution flow d, and the type and theconcentration of the common solute Xn in the feedstock solution flow aand the draw solution flow d were changed as described in Table 2.

<<Evaluation>>

-   -   (1) Evaluation of Elution Suppression Performance of Solute Xn        in Feedstock Solution Flow a

The amount of cations (cations derived from solute Xn) ionized from thesolute Xn present in the feedstock solution flow a discharged from theunit A was continuously measured using a ICP-MS (Inductively CoupledHigh Frequency Plasma-Mass Spectrometry) device manufactured by ThermoFishier Scientific, Ltd., product name “iCAP Q”.

The permeate flow rate of the solute Xn in the unit A from the start ofthe operation to the end of the operation was calculated by thefollowing formula (2). Note that the permeate flow rate of the solute Xnwas set as an amount per unit time of the solute Xn-derived cation thathas migrated from the feedstock solution flow a into the draw solutionflow d via the forward osmosis membrane o.

F′=L′/(M′×H′)  (2)

where F′ is the permeation flow rate [g/(m²× hr)] of the soluteXn-derived cation, L′ is the total amount (g) of the permeated soluteXn-derived cation, M′ is the surface area (m²) of the forward osmosismembrane o, and H′ is the operation time (hr).

From the values of the permeate flow rate F′ of the obtained solute Xn,the solute elution suppression performances evaluated on the basis ofthe following criteria are shown in Table 1.

-   -   A: the permeate flow rate of solute Xn was below the detectable        limit (0 [g/(m²× hr)]) (extremely good)    -   B: the permeate flow rate of solute Xn exceeded 0 [g/(m²× hr)]        and is 3.8 [g/(m²× hr)] or less (suitable)    -   C: the permeate flow rate of solute Xn exceeded 3.8 [g/(m²× hr)]        (poor)        (2) Evaluation of Solute Leakage Suppression Performance by        Common Solute into Draw Solution Flow d

Comparative Example 1 is an Example in which the common solute Xn wasnot contained in the draw solution flow d of Examples 1 to 5,

Comparative Example 2 is an Example in which the common solute Xn wasnot contained in the draw solution flow d of Example 6,

Comparative Example 3 is an Example in which the draw solution flow ddid not contain the common solute Xn of Examples 7 and 8, and

Comparative Examples 4 to 10 are Examples in which no common solute Xnwas contained in the draw solution flow d of Examples 9 to 15,respectively.

Regarding the corresponding combinations of the Examples and ComparativeExamples, the case in which the common solute Xn was contained in thedraw solution flow d and the case in which it was not contained werecompared by the following indicators.

Using the value of the permeate flow rate F′ of the solute Xn calculatedby the above formula (2), the value of F′ in the Examples was set as“F′1”, and the value of F′ in the Comparative Examples corresponding tothe Examples was set as “F′0”, and the solute leakage suppressionperformance value Z1 due to the common solute inclusion was calculatedby the following formula (3) and evaluated on the basis of the followingcriteria.

Z1={F′1/F′0}×100(%)  (3)

(Evaluation Criteria)

-   -   AA: the value of Z1 was 60% or less (extremely good)    -   A: the value of Z1 was greater than 60% and less than 80%        (suitable)    -   B: the value of Z1 was greater than 80% and less than 95%        (acceptable)    -   C: the value of Z1 exceeded 95%.

The evaluation results of the Comparative Examples are shown in Table 1,and the evaluation results of the Examples are shown in Table 2.

TABLE 1 Comp Comp Comp Comp Comp Comp Comp Comp Comp Comp Ex 1 Ex 2 Ex 3Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 Ex 9 Ex 10 Draw Draw Type MgCl₂ KCl MgCl₂ MgCl₂MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ Solution Substance Concentration20   20   20 20   20   20   20   20   20   20   Flow d Xm (mass %)Feedstock Solute Xn Type NaCl NaCl NaCl, KCl CaCl₂ KBr NH₄Cl KHCO₃ K₂SO₄NaNO₃ Solution KCl Flow a Initial 5.0 5.0 5.0, 5.0 5.0 5.0 5.0 5.0 5.05.0 5.0 Concentration (mass %) Unit A Elution Suppression C C C, C C C CC C C C Performance of Solute Xn

(the end of TABLE 1)

TABLE 2 Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 Draw Draw Type MgCl₂MgCl₂ MgCl₂ MgCl₂ MgCl₂ KCl MgCl₂ MgCl₂ Solution Substance Concentration20   20   20   20   20   20   20 20 Flow d Xm (mass %) Common Type NaClNaCl NaCl NaCl NaCl NaCl NaCl, KCl NaCl, KCl Solute Xn Concentration 4.82.3 1.2 0.3  0.05 2.3 2.3, 0.0 2.3, 2.9 (mass %) Feedstock Common TypeNaCl NaCl NaCl NaCl NaCl NaCl NaCl, KCl NaCl, KCl Solution Solute XnInitial 5.0 5.0 5.0 5.0 5.0 5.0 5.0, 5.0 5.0, 5.0 Flow a Concentration(mass %) Unit A Elution Suppression A A B B B A A, C A, A Performance ofCommon Solute Xn Common Solute Corresponding Comp Comp Comp Comp CompComp Comp Comp Comp Elution Ex No. Ex 1 Ex 1 Ex 1 Ex 1 Ex 1 Ex 2 Ex 3 Ex3 Suppression Eval Results AA AA AA AA B AA AA, C AA, AA Performance Ex9 Ex 10 Ex 11 Ex 12 Ex 13 Ex 14 Ex 15 Draw Draw Type MgCl₂ MgCl₂ MgCl₂MgCl₂ MgCl₂ MgCl₂ MgCl₂ Solution Substance Concentration 20   20   20  20   20   20   20   Flow d Xm (mass %) Common Type KCl CaCl₂ KBr NH₄ClKHCO₃ K₂SO₄ NaNO₃ Solute Xn Concentration 2.9 2.4 2.8 3.0 1.5 2.4 4.2(mass %) Feedstock Common Type KCl CaCl₂ KBr NH₄Cl KHCO₃ K₂SO₄ NaNO₃Solution Solute Xn Initial 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Flow aConcentration (mass %) Unit A Elution Suppression A A A A A A APerformance of Common Solute Xn Common Solute Corresponding Comp CompComp Comp Comp Comp Comp Comp Elution Ex No. Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 Ex9 Ex 10 Suppression Eval Results AA AA AA AA AA AA AA Performance

(the end of TABLE 2) Comparative Example 11

Comparative Example 11 was carried out using the feedstock solution flowconcentration system shown in FIG. 1. The forward osmosis unit Aprepared above was used as the unit A in the first step.

Water was used as the solvent b.

As the draw solution flow d, an aqueous solution containing magnesiumchloride as the draw substance Xm was used, and the magnesium chlorideconcentration in the initial draw solution flow d was set to 25% bymass.

As the feedstock solution flow a, an aqueous solution containing ethanolas the solute Xn was used, and the initial concentration thereof was setto 5.0% by mass.

In the feedstock solution flow concentration system shown in FIG. 1, thefeedstock solution flow a was flowed at a flow rate of 120 mL/min andthe draw solution flow d was flowed at a flow rate of 236 mL/min intounit A in the first step.

The diluted draw solution flow e was circulated with a circulation pumpand supplied again as the draw solution flow d.

The temperatures of the feedstock solution flow a in the unit A in thefirst step and the draw solution flow d were 25° C., and by carrying outoperations for 5 hours, concentration of the feedstock solution flow awas carried out.

Comparative Examples 12 to 20

Concentration of the feedstock solution flow a was carried out accordingto the same procedure as in Comparative Example 11, except that thetypes and concentrations of the draw substance Xm in the draw solutionflow d and the solute Xn in the feedstock solution flow a were changedas described in Table 3.

Example 16

Concentration of the feedstock solution flow a was carried out accordingto the same procedure as in Comparative Example 11, except that ethanolwas added at a concentration of 1.0% by mass as the common solute Xn inthe feedstock solution flow a together with magnesium chloride as thedraw substance Xm in the draw solution flow d.

Examples 17 to 27 and Comparative Examples 21 to 23

Concentration of the feedstock solution flow a was carried out accordingto the same procedure as in Example 16, except that the type of the drawsubstance Xm in the draw solution flow d, and the type and theconcentration of the common solute Xn in the feedstock solution flow aand the draw solution flow d were changed as described in Table 4.

Note that, even when the common solute Xn is difficult to dissolve inthe draw solution flow d, the solution was well stirred, and theconcentration of the feedstock solution flow a was evaluated by carryingout the concentration of the feedstock solution flow a while keeping theconcentration as uniform as possible.

<<Evaluation>>

Regarding the concentration of the feedstock solution flow a carried outin Comparative Examples 11 to 23 and Examples 16 to 27 described above,(1) evaluation of the elution suppressing performance of the solute Xnin the feedstock solution flow a, and (2) evaluation of the soluteleakage suppressing performance due to the common solute content in thedraw solution flow d were carried out in the same manner as inComparative Example 1, except that the measurement of the amount of thesolute Xn was carried out as follows.

The amount of solute Xn present in the diluted draw solution flow edischarged from the unit A was measured as follows, depending on whetherthe solute Xn was an organic substance or an inorganic salt.

When the solute Xn was an organic substance:

-   -   i) The case of one type of organic substance        -   The amount of solute Xn was measured as the total organic            carbon amount (TOC) using a commercially available TOC            measuring device (“TOC-5000” manufactured by Shimadzu            Corporation)    -   ii) The case of a plurality of types of organic substances        -   In addition to the TOC measurement, nuclear magnetic            resonance (NMR; model number “ECS-400”, manufactured by            Japan Electronics Co., Ltd.), and gas chromatography mass            analysis (GC/MS, model number “HP6890/5973” manufactured by            Agilent Co., Ltd.) were used for measurement, as            appropriate, to quantify each component.

When the solute Xn was an inorganic salt: measurement was carried out bythe same method as in Comparative Example 1.

The evaluation results of Comparative Examples 11 to 20 are shown inTable 3, and the evaluation results of Examples 16 to 27 and ComparativeExamples 21 to 23 are shown in Table 4.

In Table 3 and Table 4, abbreviations in the solute or common solutecolumn have the following meanings.

-   EtOH: Ethanol-   IPA: Isopropanol-   EtOAc: Ethyl acetate-   β-Cit: β-citronellol-   AcCin: Cinnamyl acetate-   AN: Acetonitrile-   Ser: L-serine

“Backflow” in the table means that the total amount of the common soluteXn in the feedstock solution flow a after concentration exceeded thetotal amount of the common solute Xn in the feedstock solution flow abefore concentration.

TABLE 3 Comp Comp Comp Comp Comp Comp Comp Comp Comp Comp Ex 11 Ex 12 Ex13 Ex 14 Ex 15 Ex 16 Ex 17 Ex 18 Ex 19 Ex 20 Draw Draw Type MgCl₂ MgCl₂MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ Solution SubstanceConcentration 25   25   25   25   25   25   25   25 25 25 Flow d Xm(mass %) Feedstock Common Type EtOH IPA EtOAc β-Cit AcCin AN Ser IPA,AN, IPA, NaCl IPA, KCl Solution Solute Xn Ser Flow a Initial 5.0 5.0 5.05.0 5.0 5.0 5.0 5.0, 5.0, 5.0, 5.0 5.0, 5.0 Concentration 5.0 (mass %)Unit A Elution Suppression C C C C C C C C, C, C C, C C, C Performanceof Common Solute Xn

(the end of TABLE 3)

TABLE 4 Comp Ex 16 Ex 17 Ex 21 Ex 18 Ex 19 Ex 20 Ex 21 Ex 22 Draw DrawType MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ MgCl₂ Solution SubstanceConcentration 25   25   25   25   25   25   25   25   Flow d Xm (mass %)Common Type EtOH EtOH IPA IPA IPA IPA IPA EtOAc Solute Xn Concentration1.0 4.5  0.001  0.05  0.15 0.3 4.5 4.0 (mass %) Feedstock Common TypeEtOH EtOH IPA IPA IPA IPA IPA EtOAc Solution Solute Xn Initial 5.0 5.05.0 5.0 5.0 5.0 5.0 5.0 Flow a Concentration (mass %) Unit A ElutionSuppression B A C B B B A A Performance of Common Solute Xn CommonSolute Corresponding Comp Comp Comp Comp Comp Comp Comp Comp CompElution Ex No. Ex 11 Ex 11 Ex 12 Ex 12 Ex 12 Ex 12 Ex 12 Ex 13Suppression Eval Results A AA C B B A AA AA Performance Comp Comp Ex 23Ex 24 Ex 25 Ex 26 Ex 27 Ex 22 Ex 23 Draw Draw Type MgCl₂ MgCl₂ MgCl₂MgCl₂ MgCl₂ MgCl₂ MgCl₂ Solution Substance Concentration 25   25   25  25   25 25 25 Flow d Xm (mass %) Common Type β-Cit AcCin AN Ser IPA, AN,IPA, NaCl IPA, KCl Solute Xn Ser Concentration  4.95 1.5 4.0 4.0 1.5,5.0, 4.6 5.5, 2.9 (mass %) 4.0, 4.0 Feedstock Common Type β-Cit AcCin ANSer IPA, AN, IPA, NaCl IPA, KCl Solution Solute Xn Ser Flow a Initial5.0 5.0 5.0 5.0 5.0, 5.0, 5.0 5.0, 5.0 Concentration 5.0, 5.0 (mass %)Unit A Elution Suppression A A A A A, A, A Backflow, Backflow,Performance of A A Common Solute Xn Common Solute Corresponding CompComp Comp Comp Comp Comp Comp Comp Elution Ex No. Ex 14 Ex 15 Ex 16 Ex17 Ex 18 Ex 19 Ex 20 Suppression Eval Results AA AA AA AA AA, AA,Backflow, Backflow, Performance AA AA AA

(the end of TABLE 4) Comparative Example 24

In Comparative Example 24, enrichment of red wine was carried out usingthe feedstock solution flow concentration system shown in FIG. 1.

The forward osmosis unit A produced above was used as unit A of thefirst step.

As the feedstock solution flow a, commercially available red wine(ethanol (EtOH) content=12.0% by volume) was used as-is. Thus, thesolvent b of the feedstock solution flow a was water. Water was used asthe solvent b of the induction liquid stream d.

As the draw solution flow d, an aqueous solution containing magnesiumchloride was used as the draw substance Xm, and the magnesium chlorideconcentration in the initial draw solution flow d was set to 32% bymass.

In the feedstock solution flow concentration system shown in FIG. 1, inthe first step, the feedstock solution flow a was flowed at a flow rateof 120 mL/min and the draw solution flow d was flowed at a flow rate of236 mL/min into unit A.

The diluted draw solution flow e was then circulated with a circulationpump and re-supplied as the draw solution flow d as-is.

The temperatures of the feedstock solution flow a in the unit A in thefirst step and the draw solution flow d were 10° C., and operation wascarried out for 1 hour.

Comparative Example 25

Concentration of the feedstock solution flow a was carried out accordingto the same procedure as in Comparative Example 24, except that ethanolwas added at a concentration of 20% by volume as the common solute Xn inthe feedstock solution flow a together with magnesium chloride as thedraw substance Xm in the draw solution flow d.

Example 28

As the draw solution flow d, an aqueous solution obtained by addingmagnesium chloride having a concentration of 32 mass % as the drawsubstance Xm and the same red wine as the feedstock solution flow a wasused, and all of the types of solute in the red wine were defined as thecommon solute Xn. The amount of red wine added to the draw solution flowd was set to be 2.0% by volume in terms of ethanol.

<<Evaluation>>

(1) Evaluation of Solute Leakage Suppression Performance by CommonSolute into Draw Solution Flow d

Comparative Example 25 and Example 28 correspond to the case where thecommon solute Xn was contained in the draw solution flow d ofComparative Example 24. Therefore, for Comparative Example 25 andExample 28, with reference to Comparative Example 24, evaluation of thesolute leakage suppressing performance due to the common solute contentinto the draw solution flow d was carried out by the following method.

Each value of F′ was obtained by carrying out “(1) Evaluation of ElutionSuppression Performance of Solute Xn in Feedstock Solution Flow a” inthe same manner as in Example 16, except that with respect to theconcentration of the feedstock solution flow a (red wine), ethanol wasselected as the solute Xn, measurement of the amount was carried out bya method described later, and the evaluation criteria were changed asfollows. Using the value of Z1 calculated by formula (2) in “(2)Evaluation of Solute Leakage Suppression Performance due to CommonSolute Inclusion into Draw Solution Flow d” in Example 16, evaluationwas carried out by the following criteria.

-   -   A: the value of Z1 was 80% or less (suitable)    -   C: the value of Z1 was greater than 80% and less than or equal        to 100% (poor)    -   Backflow: the value of Z1 exceeded 100% (extremely poor)

(2) Evaluation of Solute Component Balance Maintenance

Seven solute components, ethanol, and six organic acids (tartaric,citric, malic, lactic, succinic, and acetic acids), were selected assolutes in red wine.

Before and after concentration of red wine, the concentrations of theseseven components were measured by a method described later to determinethe composition ratio. This composition ratio was based on mass, and wasdetermined as a value normalized so that the sum of the seven componentswas 100. Thus, for the red wine before concentration and afterconcentration, the mass ratio of each component was calculated in unitsof percentage (%).

For each component, a difference (% pt) between the mass ratio (%)before concentration and the mass ratio (%) after concentration wasdetermined and evaluated by the following criteria.

-   -   A: for all seven components, the difference in the mass ratio        (%) before and after concentration was 5 (% pt) or less        (suitable)    -   C: there is one or more components with a difference in mass        ratio (%) of more than 5 (% pt) before and after concentration        (poor)

Analysis of the amount of ethanol in “(1) Evaluation of Solute LeakageSuppression Performance by Common Solute into Draw Solution Flow d” and“(2) Evaluation of Solute Component Balance Maintenance” described abovewas carried out using a rapid alcohol measurement kit manufactured byKyoto Electronics Industry Co., Ltd., and a product name “SD-700”,respectively.

Analysis of the amount of organic acid in “(2) Evaluation of SoluteComponent Balance Maintenance” described above was carried out with acalibration curve method using an HPLC.

(3) Sensory Evaluation

Pure water was added to each of the concentrated red wines (concentratedfeedstock solution flow c) obtained in Comparative Examples 24 and 25and Example 28 for dilution so that the ethanol concentration became anumerical value (12.0% by volume) before concentration to obtain aconcentrated reduced red wine.

Six evaluators were allowed to taste these concentrated reduced redwines and pre-concentrated red wines to assess astringency, sweetness,and maintenance of alcohol balance, and the wines were evaluated on thefollowing criteria:

-   -   3 points: the balance between astringency, sweetness, and        alcohol was maintained    -   1 point: the balance between astringency and sweetness was        maintained, but the balance of alcohol was lost    -   0 points: the balance between astringency, sweetness, and        alcohol was lost

For each of the Comparative Examples and the Examples, the total scoreobtained by adding the scores of the six evaluators was evaluated on thebasis of the following criteria.

-   -   A: A total score of 15 points or more (good)    -   B: A total score of 10 points to 14 points (poor)    -   C: A total score of 9 points or less (extremely poor)

The above results are shown in Table 5.

TABLE 5 Comp Ex 24 Comp Ex 25 Ex 28 Draw Draw Type MgCl₂ MgCl₂ MgCl₂Solution Substance Concentration 32   32   32   Flow d Xm (mass %)Common Type — EtOH Total Common Solute Xn Solute in Red WineConcentration — 20.0 EtOH Conversion (vol %) 2.0 Feedstock FeedstockSolution Type Red Wine Red Wine Red Wine Solution Typical Type EtOH EtOHEtOH Flow a Common Initial 12.0 12.0 12.0 Solute Xn Concentration (vol%) Common Solute Corresponding Comp Ex No. — Comp Comp Elution Ex 24 Ex24 Suppression Eval Results — C A Performance Component BalanceMaintenance C C A Sensory Evaluation C B A

(the end of TABLE 5) REFERENCE SIGN LISTS

-   a feedstock solution flow-   b solvent-   c concentrated feedstock solution flow-   d draw solution flow-   e diluted draw solution flow-   f concentrated draw solution flow-   Xn common solute-   Xm draw substance-   forward osmosis membrane-   p semipermeable membrane-   q1 heat exchanger-   q2 cooling device-   r1, r2 feed pump-   D draw solution flow-side space-   G gas phase-   L liquid phase-   R feedstock solution flow-side space

1. A feedstock solution flow concentration system, which has a firststep for counterflowing or parallel flowing a feedstock solution flowcontaining at least a solute and a solvent and a draw solution flow viaa forward osmosis membrane and transferring the solvent in the feedstocksolution flow to the draw solution flow to obtain a concentratedfeedstock solution flow, which is the feedstock solution flow which hasbeen concentrated, and a diluted draw solution flow, which is the drawsolution flow which has been diluted, wherein the draw solution flowcontains a draw substance, a common solute, and a solvent, the solventsof the feedstock solution flow and the draw solution flow both containwater, the common solute is a solute which is common between thefeedstock solution flow and the draw solution flow and is the samesolute as at least one type of solute among the solutes contained in thefeedstock solution flow, and the concentration of the common solute inthe draw solution flow is 1% to less than 100% of the concentration ofthe common solute in the feedstock solution flow.
 2. The systemaccording to claim 1, wherein the number average molecular weight of thecommon solute is 15,000 or less.
 3. The system according to claim 1,wherein the common solute is one or more selected from an ester, aterpene, a phenylpropanoid, a nucleic acid, a protein, a proteinpreparation, a vaccine, a sugar, a peptide, an amino acid, a naturalproduct pharmaceutical, a small molecule pharmaceutical, an antibiotic,an antibiotic, a vitamin, an inorganic salt, a protonic polar organiccompound, and an aprotic polar organic compound.
 4. The system accordingto claim 3, wherein the common solute comprises: a cation having atleast one element selected from the group consisting of sodium,magnesium, phosphorus, potassium, calcium, chromium, manganese, iron,cobalt, copper, zinc, selenium, and molybdenum, and an anion having atleast one element selected from the group consisting of oxygen, sulfur,nitrogen, chlorine, and iodine.
 5. The system according to claim 1,wherein the concentration of the common solute in the draw solution flowis 6% to 96% of the concentration of the common solute in the feedstocksolution flow.
 6. The system according to claim 1, wherein theconcentration of the common solute in the draw solution flow is 30% to96% of the concentration of the common solute in the feedstock solutionflow.
 7. The system according to claim 1, further comprising a secondstep in which a solvent is separated from the draw solution flow toobtain a concentrated draw solution flow, which is the draw solutionflow which has been concentrated.
 8. The system according to claim 7,further comprising means for using, in the first step, a draw solutionflow prepared by mixing the diluted draw solution flow obtained in thefirst step and the concentrated draw solution flow obtained in thesecond step.
 9. The system according to claim 7, wherein the second flowis carried out using a membrane distillation process using asemipermeable membrane.
 10. The system according to claim 1, wherein theforward osmosis membrane is used in the form of a forward osmosismembrane module constituted by fiber bundle of a plurality of hollowfibers.
 11. The system according to claim 10, wherein the forwardosmosis membrane is composite hollow fiber having an active separationlayer composed of a thin polymer membrane on an inner surface of ahollow fiber-like porous support membrane.
 12. The system according toclaim 1, wherein the feedstock solution flow is a food, pharmaceutical,pharmaceutical ingredient, pharmaceutical raw material, orpharmaceutical intermediate.
 13. The system according to claim 11,wherein the porous support membrane consists of polyethersulfone orpolysulfone, or both of them, and the active separation layer iscomposed of a thin polymer membrane of polyamide.
 14. The systemaccording to claim 3, wherein the concentration of the common solute inthe draw solution flow is 6% to 96% of the concentration of the commonsolute in the feedstock solution flow.
 15. The system according to claim3, wherein the concentration of the common solute in the draw solutionflow is 30% to 96% of the concentration of the common solute in thefeedstock solution flow.
 16. The system according to claim 3, whereinthe forward osmosis membrane is used in the form of a forward osmosismembrane module constituted by a fiber bundle of a plurality of hollowfibers.
 17. The system according to claim 16, wherein the forwardosmosis membrane is a composite hollow fiber having an active separationlayer composed of a thin polymer membrane on an inner surface of ahollow fiber-like porous support membrane.
 18. The system according toclaim 17, wherein the porous support membrane consists ofpolyethersulfone or polysulfone, or both of them, and the activeseparation layer is composed of a thin polymer membrane of polyamide.19. The system according to claim 3, wherein the concentration of thecommon solute in the draw solution flow is 6% to 96% of theconcentration of the common solute in the feedstock solution flow, theforward osmosis membrane is used in the form of a forward osmosismembrane module constituted by a fiber bundle of a plurality of hollowfibers, the forward osmosis membrane is a composite hollow fiber havingan active separation layer composed of a thin polymer membrane on aninner surface of a hollow fiber-like porous support membrane, the poroussupport membrane consists of polyethersulfone or polysulfone, or both ofthem, and the active separation layer is composed of a thin polymermembrane of polyamide.